The present invention relates to controlling the process temperature in a multi-zone thermal processor. In particular, the invention pertains to model-based predictive temperature control of multi-zone thermal processor.
A multi-zone thermal processor, such as a furnace, is widely used in semiconductor manufacturing, especially in thin film processes such as an oxidation process. The oxidation process plays a major role in wafer manufacturing, wherein an oxide layer is thermally grown or deposited on the surface of a wafer. A deposited oxide layer is produced on a wafer by providing externally supplied high-purity oxygen and silicon source in an elevated temperature environment to react and form a film on the silicon substrate. The deposition of the oxide layer is controlled and limited by the reaction of oxygen and silicon, wherein the reaction is greatly influenced by temperature, thus the growth rate of oxide is highly temperature-sensitive. Therefore, the ability to precisely control temperature in the furnace tube, where the oxidation occurs, is critical in wafer manufacturing. The thin film not only deposits on the surface of the silicon substrate, but also on the inner wall of the furnace tube. The deposited material on the inner wall hinders heat conduction and lowers the heating efficiency.
Conventionally, the temperature setting adjustment of the furnace is performed manually between two consecutive runs to compensate the heating efficiency loss resulted from deposition on the inner wall of the furnace tube. The manual adjustment is mistake-prone and time-consuming, resulting in high manufacture cost.
Hence, there is a need for a thermal process that addresses the problems arising from the existing technology.